Millstream in Stamford goes bright green after possible 'spill' | Updated: 10:28, 10 March 2021 Environmental experts have praised people for reporting the appearance of a bright green substance in Stamford's millstream. The mysterious matter was reported to Environment Agency at 1pm on Tuesday, when it was spotted coming from an outflow in Bath Row. One Mercury reader described it as "looking like Flash floor cleaner". The bright green substance in Stamford's millstream Andy Sadler, the Environment Agency's catchment coordinator for the Welland and Nene rivers, praised those who had reported it to them so that officers could investigate. The reason for the discolouration is not yet known.